Wind power is considered one of the cleanest, most environmentally friendly energy sources presently available, and wind turbines have gained increased attention in this regard. A modern wind turbine typically includes a tower, generator, gearbox, nacelle, and a rotor including one or more rotor blades. The rotor blades capture kinetic energy from wind using known foil principles and transmit the kinetic energy through rotational energy to turn a shaft coupling the rotor blades to a gearbox, or if a gearbox is not used, directly to the generator. The generator then converts the mechanical energy to electrical energy that may be deployed to a utility grid.
During operation of a wind turbine, various components of the wind turbine are subjected to various loads due to the aerodynamic wind loads acting on the blade. In particular, the rotor blades experience significant loading, and frequent changes in loading, during operation due to interaction with the wind. Changes in wind speed and direction, for example, may modify the loads experienced by the rotor blades. To reduce rotor blade loading, various methods and apparatus have been developed to enable pitching of the rotor blades during operation. Pitching generally allows the rotor blades to shed a portion of the loads experienced thereby.
In particular, many wind turbines are designed for a rated wind speed at which maximum thrust and maximum power generation occur. At higher wind speeds than the rated wind speed, the thrust is lower due to pitching of the rotor blades. Many methods are known for determining whether to pitch the rotor blades in order to reduce thrust. However, with many such currently known methods for reducing thrust, there is significant lag time between changes in wind speed being experienced by the wind turbine and pitch commands being communicated to the rotor blades. Thus, excessive loading may be experienced by the wind turbine during the lag period. Such excessive loading can weaken and damage the rotor blades, and the wind turbine in general.
Accordingly, improved methods for controlling wind turbine loading are desired in the art. For example, methods that reduce or eliminate lag time would be advantageous. In particular, methods that utilize thrust values when determining rotor blade pitch commands would be advantageous.